Treatment Response Assessment Maps to Delineate Necrosis From Tumor After Stereotactic Radiation in Brain Metastases

Inclusion Criteria: * Participants must have a histologically or cytologically confirmed solid malignancy of extracranial origin and radiographic evidence of at least one brain metastasis for which stereotactic radiation was utilized in the past. Patients with intracranial pathologic confirmation of a malignancy which originated extracranially but for which extracranial disease has not been biopsied are eligible. * Participants must have an enlarging lesion in the brain at least 4 months after prior stereotactic radiation to the same site for which neurosurgical resection is planned as routine standard of care. * Participants must be age 18 years or older. * Participants must be willing to undergo study procedures. * The effects of gadolinium / other MRI-based contrast agents on the developing human fetus are unknown. For this reason, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while she is participating in this study, she should inform her treating physician immediately. * Participants must possess the ability to understand and the willingness to sign a written informed consent document via ink on paper or via an electronic signature medium such as Adobe Sign. Exclusion Criteria: * Participants who have a contraindication to MRI (e.g. non compatible implanted metallic device for which MRI is absolutely contraindicated). * Participants who have chronic kidney disease stage IV-V or end stage renal disease. * Participants with a history of anaphylactic reactions to gadolinium. * Pregnant women are excluded from this study because gadolinium-based agents have not been proven to be safe to administer to a developing fetus. Similarly, breastfeeding women will be excluded from this study.